This invention relates to the field of the surface controllers for automatic control of subsurface safety valves used in hydrocarbon producing wells.
The desirable capability for shutting in a hydrocarbon producing well with a controllable valve at a subsurface location has long been recognized. Such desirability resides in the personnel and equipment safety benefits as well as the prevention of damage to the environment from escaping hydrocarbons. When such wells are located offshore this desirability becomes a necessity.
U.S. Pat. No. 2,518,795 to Knox discloses a subsurface safety valve that is hydraulically controlled from the surface. The well fluid pressure in the drill string or production tubing was manually controlled at the surface for remotely controlling the operation of the subsurface safety valve.
Subsequently, automatic controllers, such as disclosed in U.S. Pat. Nos. 2,785,755; 2,796,133; and 2,831,539, all to Howard EnDean, were utilized to provide automatic control of the subsurface safety valves. These automatic controllers were made responsive to conditions of wind, temperature, loss of pressure from breakage of a well head protective ring and high waves at offshore wells. Also, Natho U.S. Pat. No. RE25,109 disclosed a controller responsive to a number of conditions including a well fluid flow line break for automatically closing the subsurface safety valve.
Some typical surface located automatic control units and their remotely controlled subsurface safety valves are disclosed in the following U.S. Pat. Nos.:
______________________________________ Knox 3,305,808 Tamplen, et al 2,998,070 Keithahn 2,998,077 Bostock 2,897,415 Fredd Re 25,471 Page 3,156,300 Taylor 3,696,868 Page 3,050,132 Page 3,065,793 Page 3,216,501 Sizer Re 26,149 Taylor Re 27,464 Lewis 3,509,913 ______________________________________
The collective operative essence of these patents is to vent the increased control fluid pressure operably communicative to the subsurface valve through a single control fluid conduit which has overcomes the well fluid pressure for opening the subsurface valve and which when vented enables the subsurface valve to close and shut in the well. If a second or balance control fluid passage was used, as disclosed in Taylor U.S. Pat. No. 3,698,868, the disclosed valve could be closed by increasing the control fluid pressure in the second control fluid passage.
Relevant publications to the present invention include an article by G. M. Raulins entitled "Platform Safety by Downhole Well Control," which appeared in the March, 1972 issue of Journal of Petroleum Technology, published by the Society of Petroleum Engineers, Dallas, Texas, and the June 5, 1972 and June 12, issues of Oil and Gas Journal, published by Petroleum Publishing Company, Tulsa, Oklahoma, which in a two part article entitled "New Surface-Controlled Downhole Valves" by W. B. Bleakley considers operating features of subsurface safety valves then available from six manufacturers. More detailed descriptions of such valves and their control system may be found in the current and earlier editions of the Composite Catalog of Oil Field Equipment and Services, published by World Oil, Houston, Texas.
A Recommended Practice for Design, Installation, and Operation of Subsurface Valve Systems including automatic surface controllers was published in 1973 by the American Petroleum Institute (API). Section 3 of this API publication acknowledge that it is desirable to integrate the automatic controls of the subsurface valve with the surface valve control system, but that no automatic resets which could inadvertently reopen the subsurface safety valve may be incorporated in approved emergency shut-down system.
The controller of the present invention is preferably intended to achieve the desired object of integration with the well surface valve control system using the subsurface valves and operators disclosed in my following U.S. patents and applications but my invention is not to be considered as limited to use with these subsurface valves and operators:
______________________________________ 3,744,564 3,763,933 3,750,751 3,858,650 3,762,471 3,901,321 Serial No. 580,228, filed May 23, 1975, now Patent No. 4,019,574. ______________________________________
In general the operation of my patented valves and operators differs from that disclosed in the prior art patents of others by utilizing increased control fluid pressure in the second or hydraulic balance control line to releasably lock open the tubing retrieval valve (i.e., the valve made up in and which forms a portion of the production tubing and is therefore retrievable with the production tubing) and assist in installing and operating a supplemental through-flow-line (TFL) on wire-line retrieval type valve (i.e., the valve is run through the base of the production tubing for installation or retrieval from the subsurface location using known wire-line or TFL techniques) when the tubing retrieval valve is locked open. These tubing retrieval valves and operators also use the two control lines to achieve a hydraulic balance of the control fluid hydrostatic head which enables the subsurface valve to be set at any depth and establishes the control fluid opening pressure required to open the subsurface safety valve independent of well pressure.
Reference is hereby made to each of the aforementioned patents, applications and publications as well as those to which such specific reference is to be later made for the purpose of incorporating their entire disclosure herein as is set out in full in this specification.